operational-transform 0.6.1

use crate::OperationSeq;
use rand::prelude::*;
use rand::Rng as WrappedRng;

pub struct Rng(StdRng);

impl Default for Rng {
    fn default() -> Self {
        Rng(StdRng::from_rng(thread_rng()).unwrap())
    }
}

impl Rng {
    pub fn from_seed(seed: [u8; 32]) -> Self {
        Rng(StdRng::from_seed(seed))
    }

    pub fn gen_string(&mut self, len: usize) -> String {
        (0..len).map(|_| self.0.gen::<char>()).collect()
    }

    pub fn gen_operation_seq(&mut self, s: &str) -> OperationSeq {
        let mut op = OperationSeq::default();
        loop {
            let left = s.chars().count() - op.base_len();
            if left == 0 {
                break;
            }
            let i = if left == 1 {
                1
            } else {
                1 + self.0.gen_range(0, std::cmp::min(left - 1, 20))
            };
            match self.0.gen_range(0.0, 1.0) {
                f if f < 0.2 => {
                    op.insert(&self.gen_string(i));
                }
                f if f < 0.4 => {
                    op.delete(i as u64);
                }
                _ => {
                    op.retain(i as u64);
                }
            }
        }
        if self.0.gen_range(0.0, 1.0) < 0.3 {
            op.insert(&("1".to_owned() + &self.gen_string(10)));
        }
        op
    }
}